linux-kernel - Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update ucode on Intel's CPU

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Message-ID: <50D29249.1090109@linux.intel.com>
Date:	Wed, 19 Dec 2012 20:21:29 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Jacob Shin <jacob.shin@....com>
CC:	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Yinghai Lu <yinghai@...nel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update
 ucode on Intel's CPU

On 12/19/2012 08:16 PM, Jacob Shin wrote:
> 
> Not exactly sure why the wierd boundaries, I'll have to ask the BIOS
> side folks to be sure. But if I were to guess ..
> 
> Here is the NUMA spew out, physically there is 128 GB connected to
> each memory controller node. The PCI MMIO region starts at 0xc8000000.
> 4 GB - 0xc8000000 = 0x3800000 (896 MB). So we loose 896 MB due to PCI
> MMIO hole, so the first node ends at 128 GB + 896 MB to talk to all of
> 128 GB off of the first memory controller, and hence the weird 896 MB
> offset.
> 

It would obviously be better if the slack were at the end of the total
memory, instead of end of the < 1T range.  If the PCI MMIO hole were a
power of 2 (e.g. 1G) that would also reduce the likelihood of problems
and reduce MTRR pressure.

	-hpa

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